1. Field of the Invention
This invention relates to the field of earth working equipment for landscaping, leveling, finish grading, cutting and spreading dirt, sand, gravel and the like. More particularly, the invention relates to such an apparatus capable of being towed by a light vehicle.
2. Description of the Prior Art
Ground surface grading devices for leveling and finish grading of rough terrain after preliminary smoothing by heavy equipment, such as a bulldozer or heavy tractor, have been available for many years. Grading equipment that can be shifted from one vehicle to another for greater operational flexibility is known and available commercially. Nevertheless, heavy-duty equipment, such as an earthmover or commercial tractor, must tow these devices.
Many potential operators of grading equipment, private individuals, businesses and local governments, do not have ready access to, or need heavy equipment to perform their work. But most operators usually have a vehicle such as a light truck, pickup truck, or small tractor that can be used for landscaping, ground leveling, finish grading, earth cutting, and for spreading dirt, sand, gravel and other such material at worksites, playing fields, gravel or dirt driveways and pathways, drainage culverts, and motor-cross tracks.
Most earth moving equipment is operated hydraulically via lines extending from the towing vehicle. Large equipment requires a reservoir of several gallons of hydraulic fluid for proper operation. Heavy-duty towing equipment may be able to provide such capacity, but vehicles normally employed by a private user cannot readily accommodate a large supplemental reservoir of hydraulic fluid. Instead, light vehicles must be modified to provide proper operation of the conventional towable earth working equipment, provided that the vehicles have the capacity to haul them. Such modifications increase the cost of the equipment and compromise operation of the vehicle. A more suitable towed apparatus would operate using hydraulic systems and other actuation equipment readily available to owners of light vehicles.
U.S. Pat. No. 5,289,880 describes a towable road grader for use behind a small vehicle, such as a pickup truck, the grader being either centered directly behind the towing vehicle or offset from center. A support frame secures a tending tool, a wheel frame pivots the rear towing wheels either toward or away from the support frame, and an attachment frame joins the other two frames to a hitch on the towing vehicle. The attachment frame keeps the support frame parallel to the plane of the underlying roadway surface as the support frame is raised or lowered. The attachment frame pivots upward when the tending tool is lowered to the roadway surface. As the wheels are raised and lowered, the cutting blade is raised and lowered. However, raising and lowering the wheels does not change the angular position of the blade relative to a horizontal plane or the ground surface. If the inclination of the blade were so changed, it would facilitate its engagement with the soil as ground conditions change and as the work requires.
U.S. Pat. No. 6,347,670 describes a device for modifying the ground surface by removing soil, moving the soil to a new location, and filling low areas. It includes a frame carried by wheels, a tongue mounted to the frame for attachment to a tractor, a cutting blade mounted on the frame, and a bucket pivotally mounted to the frame to receive soil cut by the blade. The wheels are pivotally mounted to the frame for movement about the back wall and floor of the bucket between a first position and second position. The position of the wheels is not adjustable between the extremities of travel between the first and second positions.
It would be desirable to have a device that is towable behind a light vehicle for moving over rugged ground or a smoother surface on which soil, sand, or gravel are to be moved or graded. It is desired to have an earth working apparatus that includes a grader supported on a frame by wheels that can be raised and lower over an adjustable range. Preferably, the grader would include a cutting blade that is easily raised and lowered as the wheels are raised and lowered, and its angular disposition adjustable relative to the horizontal. Also, it is preferable to have a grader that can be easily configured to make a number of different profiles for various working sites, such as a level field for sporting events or a contoured ditch for drainage.